The Collaborative International Dictionary of English v.0.48:

Backsword \Back"sword`\, n. [2d back, n. + sword.]
   1. A sword with one sharp edge.
      [1913 Webster]

   2. In England, a stick with a basket handle, used in rustic
      amusements; also, the game in which the stick is used.
      Also called singlestick. --Halliwell.
      [1913 Webster]

WordNet (r) 3.0 (2006):

backsword
    n 1: a stick used instead of a sword for fencing [syn:
         singlestick, fencing stick, backsword]
    2: a sword with only one cutting edge